1. Field of the Invention
This invention relates to a control apparatus for a general-purpose internal combustion engine, particularly to an apparatus for controlling warm-up operation of a general-purpose internal combustion engine.
2. Description of the Related Art
Conventionally, in general-purpose internal combustion engines used as prime movers in generators, agricultural machines and various other equipment conducting engine, warm-up operation is conducted since engine starting for making the engine speed stable to prevent engine stall due to abrupt opening and closing of a throttle valve as taught by Japanese Laid-Open Patent Application No. Hei 5(1993)-59992 (paragraphs 0035, 0036, 0042 to 0044, FIGS. 10, 15, etc.).
However, when a fuel quantity is kept increasing until the engine has been completely warmed up as described in the reference '992, although engine stall can be surely prevented, the rate of fuel consumption and also the emission performance degrades disadvantageously. Therefore, it is preferable to complete the warm-up operation with increased fuel in a short period of time.
It is also known to start the engine warm-up operation by closing a choke valve to a position corresponding to ambient temperature for increasing fuel quantity and to finish it by gradually opening the choke valve to a fully-opened position as taught by Japanese Laid-Open Patent Application No. Hei 7(1995)-77106 (paragraphs 0036, 0041 to 0044, FIGS. 3, 4, etc.).
However, since an appropriate or optimal time period of warm-up differs depending on ambient temperature or condition of the engine, if the warm-up operation is conducted by regulating the choke valve position based solely on the ambient temperature, i.e., by determining the warm-up time period based solely on the ambient temperature as disclosed in the reference '106, the warm-up time period could be inappropriate depending on the condition of the engine. This also leads to the degradation of the rate of fuel consumption and occurrence of engine stall.